1. Field of the Invention
The present invention relates to a semiconductor device using a plurality of spherical members, such as spherically shaped semiconductors. More particularly, the present invention relates to a stacking structure of the spherically shaped semiconductors.
2. Description of the Related Art
Conventionally, in manufacturing a semiconductor device, various semiconductor elements have been formed on the surface of a wafer-like semiconductor substrate. In contrast, Ball Semiconductor, Co., Ltd. has disclosed a technology for manufacturing a semiconductor device with the use of a spherical semiconductor having semiconductor elements formed on the surface of a spherical semiconductor material (silicon) in xe2x80x9cNikkei Micro Device (No. 157)xe2x80x9d, issued on Jul. 1, 1998, and in U.S. Pat. Nos. 5,877,943 and 5,955,776. The spherical semiconductor with semiconductor elements formed thereon may constitute a spherical integrated circuit (IC), for example. Since the spherical semiconductor has a higher area-to-volume ratio compared to the wafer-like semiconductor substrate, it has the advantage that a wider surface area can be achieved with less semiconductor material. Here, the spherical semiconductor material can be obtained by, for example, melting a granular polycrystalline semiconductor material having a diameter of about 1 mm in an argon atmosphere at 1000xc2x0 C. to 10000xc2x0 C. using inductively coupled plasma, and by mono-crystallizing the molten material.
In addition, in order to form various semiconductor elements on the surface of the spherical semiconductor material, for example, an exposure method shown in FIG. 5 is used. According to this exposure method, light passing through a mask is reflected by mirrors 31, 32, and 33, which are disposed to encircle a spherical semiconductor material 10, toward the spherical semiconductor material 10, hereby the surface of the spherical semiconductor material 10 is subjected to full plate exposure. In addition, in an etching step or a film deposition step, etching or film deposition is performed by allowing an etching gas or raw material gas and the spherical semiconductor material 10 to flow through a tube.
In addition, the spherical semiconductor having various semiconductor elements formed on the spherical semiconductor material 10 in this way may be used to form a semiconductor device by combining a number of spherical semiconductors 11, stacked on a substrate 15 in multiple stages, as shown in FIG. 6, for example. According to this semiconductor device, spherical semiconductors 11 are stacked directly above other spherical semiconductors 11 aligned on a lower stage, and each of the spherical semiconductors 11 is electrically connected to the vertically and horizontally positioned spherical semiconductors 11 to perform a predetermined operation. Here, a semiconductor element having a predetermined function is formed on each of the spherical semiconductors 11, and each of the spherical semiconductors 11 performs a function such as that of a microprocessor, an input-output interface, a counter, logic, a RAM, or a ROM, for example.
The semiconductor device using such spherical semiconductors 11 will be mounted on various devices in the future, but many problems are yet to be solved. For example, when the semiconductors 11 are used, since they are spherical in shape, they are not easily positioned even if stacked in multiple stages, as shown in FIG. 6.
Therefore, it is an object of the present invention to overcome the aforementioned problems.
In consideration of the above problem, it is an object of the present invention to provide a semiconductor device in which it is easy to stack at predetermined positions a plurality of spherical semiconductors, each having semiconductor elements or wiring formed on the surface of a spherical semiconductor material.
Accordingly, the present invention provides a semiconductor device in which a plurality of spherical members are easily stacked at predetermined positions. To this end, the semiconductor device comprises four spherical members, at least one of the spherical members comprises a spherically shaped semiconductor material and a semiconductor element formed thereon. In addition, one of the spherical members is in contact with the other three spherical members.
Specifically, there is provided a semiconductor device including a plurality of spherical members stacked in multiple stages. At least one of the plurality of spherical members is formed of a semiconductor material and includes a semiconductor element or wiring formed on a surface of the semiconductor material. The plurality of spherical members includes at least one set of four spherical members arranged such that a regular triangular pyramid is formed by imaginary lines connecting the centers of said four spherical members. The four spherical members includes three spherical members- aligned so as to be substantially in contact with one another in a lower stage of the multiple stages and one spherical member is stacked, in an upper stage of the multiple stages, on the three spherical members.
According to the present invention, one of the spherical members, stacked on the upper stage, is positioned by the other three spherical members, on the lower stage by, in contrast with the conventional technology, utilizing the fact that the members are spherical in shape. Preferably, three spherical members of four spherical members are arranged so as to be in contact or substantially in contact with one another, and one spherical semiconductor is stacked in a depression that is formed in the center of the three spherical semiconductors. This positioning provides great stability for a structure stacking the four spherical members in three dimensions, and the three spherical members on the lower stage position the spherical member on the upper stage. Therefore, a plurality of spherical members can be stacked at predetermined positions easily. To stack these four spherical members efficiency, or to stack a plurality of sets of spherical members, preferably, each of the spherical members has substantially same size and the members are in contact or substantially in contact with each other.
Here, in the case of stacking more than four spherical members, a plurality of sets of four spherical members may be included such that the imaginary lines connecting the centers of each set of four spherical members form a regular triangular pyramid.
In another aspect of the present invention, a semiconductor device comprises a set of spherical members including four spherical members. The set has at least a first spherical member comprising a spherically shaped semiconductor material and a semiconductor element formed thereon. Also, one of the spherical members is in contact with the other three spherical members so as to be supported thereby. The set of spherical members also has at least one spherical member without a semiconductor element formed thereon, referred to herein as a connecting spherical member.
In an embodiment of the present invention, at least one connecting spherical member formed without a semiconductor element is used to increase the possible combinations for electrically connecting the spherical semiconductors stacked in three dimensions. In this case, a wiring pattern is preferably formed on the connecting spherical member. Therefore, a connecting spherical member performs the function of electrically connecting a plurality of other spherical members.
In another aspect of the present invention, in the plurality of spherical members, a dummy spherical member may be included that performs the function of filling gaps when stacking in multiple stages spherical semiconductors that each have a semiconductor element formed thereon. A semiconductor element is not formed on the dummy spherical member. With this configuration, since the dummy spherical member fills a void even where a spherical semiconductor 11 does not have to exist from the viewpoint of an electrical connection, no gap is formed. Therefore, at any place where the spherical members are stacked, a structure is realized such that one spherical member is stacked in a depression that is formed in the center of three spherical members aligned so as to be in contact or substantially in contact with one another.
Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.